Romans 4:13, 16-18
13The promise to Abraham and his descendants, that they should inherit the world, did not come through the law but through the righteousness of faith. 16That is why it depends on faith, in order that the promise may rest on grace and be guaranteed to all his descendants -- not only to the adherents of the law but also to those who share the faith of Abraham, for he is the father of us all, 17as it is written, "I have made you the father of many nations" -- in the presence of the God in whom he believed, who gives life to the dead and calls into existence the things that do not exist. 18In hope he believed against hope, that he should become the father of many nations; as he had been told, "So shall your descendants be."
Psalms 105:6-9, 42-43
6O offspring of Abraham his servant, sons of Jacob, his chosen ones! 7He is the LORD our God; his judgments are in all the earth. 8He is mindful of his covenant for ever, of the word that he commanded, for a thousand generations, 9the covenant which he made with Abraham, his sworn promise to Isaac, 42For he remembered his holy promise, and Abraham his servant. 43So he led forth his people with joy, his chosen ones with singing.
8"And I tell you, every one who acknowledges me before men, the Son of man also will acknowledge before the angels of God; 9but he who denies me before men will be denied before the angels of God. 10And every one who speaks a word against the Son of man will be forgiven; but he who blasphemes against the Holy Spirit will not be forgiven. 11And when they bring you before the synagogues and the rulers and the authorities, do not be anxious how or what you are to answer or what you are to say; 12for the Holy Spirit will teach you in that very hour what you ought to say."